Mediterranean diet and health status: an updated meta-analysis and a proposal for a literature-based adherence score

Abstract

Objective: To update previous meta-analyses of cohort studies that investigated the association between the Mediterranean diet and health status and to utilize data coming from all of the cohort studies for proposing a literature-based adherence score to the Mediterranean diet.

Design: We conducted a comprehensive literature search through all electronic databases up to June 2013.

Setting: Cohort prospective studies investigating adherence to the Mediterranean diet and health outcomes. Cut-off values of food groups used to compute the adherence score were obtained.

Subjects: The updated search was performed in an overall population of 4 172 412 subjects, with eighteen recent studies that were not present in the previous meta-analyses.

Results: A 2-point increase in adherence score to the Mediterranean diet was reported to determine an 8 % reduction of overall mortality (relative risk = 0·92; 95 % CI 0·91, 0·93), a 10 % reduced risk of CVD (relative risk = 0·90; 95 % CI 0·87, 0·92) and a 4 % reduction of neoplastic disease (relative risk = 0·96; 95 % CI 0·95, 0·97). We utilized data coming from all cohort studies available in the literature for proposing a literature-based adherence score. Such a score ranges from 0 (minimal adherence) to 18 (maximal adherence) points and includes three different categories of consumption for each food group composing the Mediterranean diet.

Conclusions: The Mediterranean diet was found to be a healthy dietary pattern in terms of morbidity and mortality. By using data from the cohort studies we proposed a literature-based adherence score that can represent an easy tool for the estimation of adherence to the Mediterranean diet also at the individual level.

Fig. 1

Forest plot for updated meta-analysis on greater adherence score to the Mediterranean diet (2-point increase) and overall mortality risk. Plotted are the relative risk (RR; represented by ▪, with the symbol size proportional to the weight in meta-analysis) and the 95 % confidence interval (represented by horizontal bars), with the summary measure (represented by - - - - - and ⧫, with the associated 95 % confidence interval indicated by the symbol width) and the line of no effect (——)

Fig. 2

Forest plot for updated meta-analysis on greater adherence score to the Mediterranean diet (2-point increase) and cardiovascular incidence and/or mortality risk. Plotted are the relative risk (RR; represented by ▪, with the symbol size proportional to the weight in meta-analysis) and the 95 % confidence interval (represented by horizontal bars), with the summary measure (represented by - - - - - and ⧫, with the associated 95 % confidence interval indicated by the symbol width) and the line of no effect (——)

Fig. 3

Forest plot for updated meta-analysis on greater adherence score to the Mediterranean diet (2-point increase) and cancer incidence and/or mortality risk. Plotted are the relative risk (RR; represented by ▪, with the symbol size proportional to the weight in meta-analysis) and the 95 % confidence interval (represented by horizontal bars), with the summary measure (represented by - - - - - and ⧫, with the associated 95 % confidence interval indicated by the symbol width) and the line of no effect (——)

Fig. 4

Literature-based adherence score to the Mediterranean diet (range: 0–18 points). Portion sizes derive from the calculation of mean value of weighted medians (or means) ±2 sd coming from all the cohort studies reported in Tables 1 and 2